The present disclosure relates to refrigeration. More particularly, it relates to ejector refrigeration systems.
Ejectors are used as expansion devices in vapor compression refrigeration systems. Ejectors may be used to recover work to allow operational conditions and/or configurations not available with a traditional expansion device. Earlier proposals for ejector refrigeration systems are found in U.S. Pat. Nos. 1,836,318 and 3,277,660.
A typical ejector utilizes a motive (primary) flow of fluid to entrain a secondary (suction) flow. A common ejector configuration includes a motive (primary) inlet coaxial with a downstream outlet. The ejector also has a secondary inlet. The exemplary primary inlet is the inlet of a motive (primary) nozzle nested within an outer member. The outlet is the outlet of the outer member. The primary flow enters the primary inlet and then passes into a convergent section of the motive nozzle. It then passes through a throat section and an expansion (divergent) section and through an outlet of the motive nozzle. The motive nozzle accelerates the primary flow and decreases the pressure of the primary flow. The secondary inlet forms an inlet of the outer member and may be a lateral port. The pressure reduction caused to the primary flow by the motive nozzle helps draw the secondary flow into the outer member.
The outer member includes a mixer having a convergent section and an elongate throat or mixing section. The outer member also has a divergent section or diffuser downstream of the elongate throat or mixing section. The motive nozzle outlet is positioned within the convergent section. As the primary flow exits the motive nozzle outlet, it begins to mix with the secondary flow with further mixing occurring through the mixing section which provides a mixing zone.
In transcritical refrigeration operation, the primary flow may typically be supercritical upon entering the ejector and subcritical upon exiting the motive nozzle. The secondary flow may be is gaseous (or a mixture of gas with a smaller amount of liquid) upon entering the secondary inlet port. The resulting combined flow may be a liquid/vapor mixture and decelerate and recover pressure in the diffuser while remaining a mixture.